There are plethora of books on castle I will list 2 that got high ratings on Amazon.
日本100名城公式ガイドブック―日本の文化遺産「城」を見に行こう (歴史群像シリーズ) [単行本]
戦国の城 (歴史群像シリーズ特別編集) [ムック]
I can't vouch for the credibility of these books as I don't own them...
I've got them both, plus about 17 others and it depends on what you want. They are useful certainly but only cover certain aspects of castle construction.
cheers
James